Chapter 20

Rapid Sequence Intubation

Calvin A. Brown III and Ron M. Walls

INTRODUCTION

Definition

Rapid sequence intubation (RSI) is the administration, after preoxygenation and patient optimization, of a potent induction agent followed immediately by a rapidly acting neuromuscular blocking agent (NMBA) to induce unconsciousness and motor paralysis for tracheal intubation. The technique is predicated on the fact that the patient has not fasted before intubation and, therefore, is at risk for aspiration of gastric contents. The preoxygenation phase begins before drug administration and permits a period of apnea to occur safely between the administration of the drugs and intubation of the trachea without the need for positive-pressure ventilation. Likewise, preintubation optimization is a step focused on maximizing patient hemodynamics and overall physiology before RSI drugs are given and is designed predominantly to protect against circulatory collapse during or immediately after the intubation. In other words, the purpose of RSI is to render the patient unconscious and paralyzed and then to intubate the trachea, with the patient as oxygenated and physiologically optimized as possible, without the use of bag-mask ventilation, which may cause gastric distention and increase the risk of aspiration. The Sellick maneuver (posterior pressure on the cricoid cartilage to occlude the esophagus and prevent passive regurgitation) has been shown to impair glottic visualization in some cases, and the evidence supporting its use is dubious, at best. As in the fourth edition, we no longer recommend routine use of this maneuver during emergency intubation.

Indications and Contraindications

RSI is the cornerstone of emergency airway management and is the technique of choice when emergency intubation is indicated, and the patient does not have difficult airway features felt to contraindicate the use of an NMBA (see Chapters 2 and 3). When a contraindication to succinylcholine is present, rocuronium should be used as the NMBA (see Chapter 22). Some practitioners eschew the use of succinylcholine and routinely use rocuronium for all intubations; this is a matter of preference, for there are both pros and cons to this approach.

RSI can be thought of as a series of discrete steps, referred to as the seven Ps. Although conceptualizing RSI as a series of individual actions is helpful when teaching or planning the technique, most emergency intubations require that several steps, especially leading up to tube placement, occur simultaneously. In this latest edition, preintubation optimization has replaced pretreatment as the third “P” in RSI because a critical reappraisal of the available evidence behind pretreatment agents has failed to identify high-quality studies or clear patient benefit, except when these agents are used to optimize the patient’s physiologic state to better tolerate the medications, intubation, and positive-pressure ventilation. Otherwise, adding unnecessary drugs contributes to procedural inefficiencies and introduces the potential for adverse drugs reactions and dosing errors. The seven Ps of RSI are shown in Box 20-1.

Preparation

Before initiating the sequence, the patient is thoroughly assessed for difficulty of intubation (see Chapter 2). Fallback plans in the event of failed intubation are established, and the necessary equipment is located. The patient is in an area of the emergency department that is organized and equipped for resuscitation. Cardiac monitoring, BP monitoring, and pulse oximetry should be used in all cases. Continuous waveform capnography provides additional valuable monitoring information, particularly after intubation, and should be used whenever possible. The patient should have at least one, and preferably two, secure, well-functioning intravenous (IV) lines. Pharmacologic agents are drawn up in properly labeled syringes. Vital equipment is tested. A video laryngoscope, if available, should be brought to the bedside and tested for image clarity whether or not it is to be used on first attempt. If a direct laryngoscope is to be used, the blade of choice is affixed to the laryngoscope handle and clicked into the “on” position to ensure that the light functions and is bright. The endotracheal tube (ETT) of the desired size is prepared, and the cuff is tested for leaks. If difficult intubation is anticipated, a tube 0.5 mm or less in internal diameter (ID) should also be prepared. Selection and preparation of the tube, as well as the use of the intubating stylet and bougie, are discussed in Chapter 13. Throughout this preparatory phase, the patient is receiving preoxygenation and optimization measures, if appropriate, as described in the next two sections.

Preoxygenation

Preoxygenation is essential to the “no bagging” principle of RSI. Preoxygenation is the establishment of an oxygen reservoir within the lungs, blood, and body tissue to permit several minutes of apnea to occur without arterial oxygen desaturation. The principal reservoir is the functional residual capacity in the lungs, which is approximately 30 mL per kg. Administration of 100% oxygen for 3 minutes replaces this predominantly nitrogenous mixture of room air with oxygen, allowing several minutes of apnea time before hemoglobin saturation decreases to <90% (Fig. 20-1). Similar preoxygenation can be achieved much more rapidly by having the patient take eight vital capacity breaths (the greatest volume breaths the patient can take) while receiving 100% oxygen.

Obese patients are best preoxygenated when placed upright and oxyhemoglobin desaturation is significantly delayed if oxygen is continuously administered at 5 to 15 L per minute by nasal cannula throughout the intubation sequence. The highest flow rate the patient will tolerate, with a goal of 15 L per minute, should be used. The evidence for “apneic oxygenation” will be presented at the end of this chapter. Even in non-obese patients, desaturation can be mitigated through continuous administration of oxygen at 5 to 15 L per minute during apnea. There is little downside to providing nasal cannula oxygen during the apneic phase of intubation for all emergency department intubations, however we consider it essential for patients predicted to rapidly desaturate.

The time to desaturation for an individual patient varies. Children, morbidly obese patients, chronically ill patients (especially those with cardiopulmonary diseases), and late-term pregnant women desaturate significantly more rapidly than an average healthy adult.

Note the bars indicating recovery from succinylcholine paralysis on the bottom right of Figure 20-1. This demonstrates the fallacy of the oft-cited belief that a patient will recover sufficiently from succinylcholine-induced paralysis to breathe on his or her own before sustaining injury from hypoxemia, even if intubation and mechanical ventilation are both impossible. Although many healthy patients with normal body habitus will recover adequate neuromuscular function to breathe on their own before catastrophic desaturation, many others, including almost all children and a majority of patients intubated for emergency conditions, will not, and even those who do are dependent on optimal preoxygenation before paralysis.

A healthy, fully preoxygenated 70-kg adult will maintain oxygen saturation at >90% for 8 minutes, whereas an obese adult will desaturate to 90% in <3 minutes. A 10-kg child will desaturate to 90% in <4 minutes. The time for desaturation from 90% to 0% is even more important and is much shorter. The healthy 70-kg adult desaturates from 90% to 0% in <120 seconds, and the small child does so in 45 seconds. A late-term pregnant woman is a high oxygen user, has a reduced functional residual capacity, and has an increased body mass, so she desaturates quickly in a manner analogous to that of the obese patient. Particular caution is required in this circumstance because both the obese patient and the pregnant woman may also be difficult to intubate and to bag-mask ventilate.

• FIGURE 20-1. Time to Desaturation for Various Patient Circumstances. (From Benumof J, Dagg R, Benumof R. Critical hemoglobin desaturation will occur before return to an unparalyzed state following 1 mg/kg IV succinylcholine. Anesthesiology. 1997;87:979.)

Most emergency departments do not use systems that are capable of delivering 100% oxygen. Typically, emergency department patients are preoxygenated using the “100% non-rebreather mask,” which delivers approximately 65% to 70% oxygen depending on fit, oxygen flow rate, and respiratory rate (see Chapter 5). In physiologically well patients in whom difficult intubation is not anticipated, this percentage is often sufficient and adequate preoxygenation is achieved. However, higher inspired fractions of oxygen are often desirable and can be delivered by active breathing through the demand valve of bag-mask systems equipped with a one-way exhalation valve. Recent evidence suggests preoxygenation performed with an Ambu bag is superior to face mask oxygen. Specially designed high-concentration oxygen delivery devices such as high-flow nasal cannula (HFNC), capable of providing both positive end-expiratory pressure and up to 70 L per minute of oxygen flow through specially designed nasal prongs, have been used for preparatory oxygenation, although the role of HFNC for emergency department (ED) patients is not defined. Available evidence from intensive care unit patients is mixed on its ability to prevent desaturation during urgent inpatient intubations. Oxygen delivery is discussed in detail in Chapter 5. The use of pulse oximetry throughout intubation enables the physician to monitor the level of oxygen saturation eliminating guesswork.

Preintubation Optimization

Patients may be challenging to intubate for anatomic reasons such as airway obstruction or reduced neck mobility. Additionally, overall airway management can be made more complex by dramatic perturbations in vital signs and patient physiology. Although septic shock, severe myocardial depression, or an inability to preoxygenate in and of themselves do not make the act of laryngoscopy and tracheal tube placement more difficult, they can contribute to operator stress and patient morbidity by drastically compressing the time available to safely intubate or by placing the patient at risk for hypoxic injury or peri-intubation circulatory collapse after receiving induction agents. Preintubation optimization involves identifying and mitigating areas of cardiopulmonary vulnerability that may complicate resuscitative efforts, even if tracheal intubation goes quickly and smoothly. If the need for intubation is not immediate, then abnormal hemodynamic parameters should be normalized as much as possible prior to intubation. A simple example of this would be the insertion of a chest tube for a patient with tension pneumothorax to improve oxygenation and perfusion before initiating intubation. Common aspects of abnormal patient physiology that should be identified and addressed during this step are shown in Box 20-2. The most commonly encountered physiologic problem is hypotension. Bleeding, dehydration, sepsis, and primary cardiac pathology are common emergency conditions that can complicate patient management, despite successful placement of the ETT. All induction agents can potentiate peripheral vascular dilation and myocardial depression and patients who present with depressed cardiac function, low intravascular volume, or poor vascular tone can suffer profound refractory shock or circulatory collapse after RSI drugs are administered, particularly when positive-pressure ventilation further compromises venous return. Isotonic fluids, blood products, and pressor agents may be used, time permitting, to support blood pressure and increase pharmacologic options for RSI. Oxygenation efforts are reassessed during this step and escalated if necessary. Hypertensive crises can also be prevented or treated with sympatholytic agents (fentanyl) prior to laryngeal manipulation and tube placement, both known to result in a sympathetic surge during intubation.

These steps should be addressed for all intubations when time and resources allow.

ICP = Intracranial pressure

Bi-PAP = Bi-level positive airway pressure

CPAP = Continuous positive airway pressure

Paralysis with Induction

In this phase, a rapidly acting induction agent is given in a dose adequate to produce prompt loss of consciousness (see Chapter 21). Administration of the induction agent is immediately followed by the NMBA, usually succinylcholine (see Chapter 22). If succinylcholine is contraindicated, rocuronium should be used. Both the induction agent and the NMBA are given by IV push. RSI does not involve the slow administration of the induction agent or a titration-to-end point approach. The sedative agent and dose are selected with the intention of rapid IV administration of the drugs. Although rapid administration of the induction agent can increase the likelihood and severity of side effects, especially hypotension, the entire technique is predicated on rapid loss of consciousness, rapid neuromuscular blockade, and a brief period of apnea without interposed assisted ventilation before intubation. Therefore, the induction agent is given as a rapid push followed immediately by a rapid push of the NMBA. Within several seconds of the administration of the induction agent and NMBA, the patient will begin to lose consciousness, and respiration will decline, and then cease.

Positioning

After 20 to 30 seconds, the patient is induced, apneic and becoming flaccid. If succinylcholine has been used as the NMBA, fasciculations will be observed during this time. The oxygen mask and nasal cannula used for preoxygenation remain in place to prevent the patient from acquiring even a partial breath of room air. At this point, the patient is positioned optimally for intubation, with consideration for cervical spine immobilization in trauma. The bed should be at sufficient height to comfortably perform laryngoscopy, although this is much more an issue for direct than for video laryngoscopy. The patient should be transitioned fully to the head of the bed and, if appropriate, the head should be elevated and extended. Some patients will be sufficiently compromised that they require assisted ventilation continuously throughout the sequence to maintain oxygen saturations over 90%. Such patients, especially those with profound hypoxemia, are ventilated with bag and mask at all times except when laryngoscopy is occurring. Patients predicted to rapidly desaturate (morbid obesity, suboptimal starting oxygen saturations) will maintain high oxygen saturations longer if they receive oxygen at 5 to 15 L per minute through nasal cannula throughout laryngoscopy. The highest nasal cannula flow rate the patient can tolerate while awake should be used. The flow rate can then be increased to as much as 15 L per minute after the patient is unconscious. When bag-mask ventilation is performed on an unresponsive patient, the application of Sellick maneuver may minimize the volume of gases passed down the esophagus to the stomach, possibly decreasing the likelihood of regurgitation.

Placement with Proof

At 45 seconds after the administration of the succinylcholine, or 60 seconds if rocuronium is used, test the patient’s jaw for flaccidity and intubate. Strict attention to robust preoxygenation endows most patients with minutes of safe apnea time, allowing the intubation to be performed gently and carefully. Multiple attempts, if needed, are often possible without any need to provide additional oxygenation by bag and mask. Tube placement is confirmed as described in Chapter 12. End-tidal carbon dioxide (ETCO₂) detection is mandatory. A capnometer, such as a colorimetric ETCO₂ detector, is sufficient for this purpose. We recommend the use of continuous quantitative capnography, if available, as this provides additional and ongoing information.

Postintubation Management

After placement is confirmed, the ETT is secured in place. Mechanical ventilation should be initiated as described in Chapter 7. A chest radiograph should be obtained to assess pulmonary status and ensure that mainstem intubation has not occurred. Hypotension is common in the postintubation period and is often caused by diminished venous blood return as a result of the increased intrathoracic pressure that attends mechanical ventilation, exacerbated by the hemodynamic effects of the induction agent. Although this form of hypotension is often self-limited and responds to IV fluids, persistent or profound hypotension may indicate a more ominous cause, such as tension pneumothorax or impending circulatory collapse. If significant hypotension is present, the management steps in Table 20-1 should be considered.

Long-term sedation is generally indicated. The intubating clinician should pay close attention to postintubation sedation as recent ED-based research suggests that sedation is either not administered or given in low doses in as many as 18% of patients intubated after using neuromuscular blockade. Long-term paralysis, however, is generally avoided, except when necessary. Use of a sedation scale, such as the Richmond Agitation Sedation Scale, to optimize patient comfort helps guide decision-making regarding the necessity of neuromuscular blockade (Box 20-3). Sedation and analgesia are administered to reach the desired level, and neuromuscular blockade is used only if the patient then requires it for management. Use of a sedation scale prevents the use of neuromuscular blockade for patient control when the cause of the patient’s agitation is inadequate sedation. A sample sedation protocol is shown in Figure 20-2. Maintenance of intubation and mechanical ventilation requires both sedation and analgesia, and these can be titrated to patient response. Propofol has become the agent of choice for ongoing sedation in mechanically ventilated patients, especially for those with neurologic conditions. Propofol is preferable because it can be discontinued or decreased with rapid recovery of consciousness. Propofol infusion can be started at 25 to 50 µg/kg/minute and titrated. An initial bolus of 0.5 to 1 mg per kg may be given if rapid sedation is desired. Analgesia is required, as above, because propofol is not an analgesic. Secondary sedation strategies might include midazolam 0.1 to 0.2 mg per kg, combined with an analgesic such as fentanyl 2 µg per kg, morphine 0.2 mg per kg, or hydromorphone (Dilaudid) 0.03 mg per kg. Fentanyl may be preferable because of its superior hemodynamic stability. When an NMBA is required, a full paralytic dose should be used (e.g., vecuronium 0.1 mg per kg). Sedation and analgesia are difficult to titrate when the patient is paralyzed, and “topping up” doses should be administered regularly, before physiologic stress (hypertension and tachycardia) is evident.

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Noninvasive Mechanical Ventilation Distorted Airways and Acute Upper Airway Obstruction The Patient with Prolonged Seizure Activity Blind Intubation Techniques The Difficult Pediatric Airway Video Laryngoscopy

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